Pawl arrangement for hoist



Aug. 6, 1963 F.J.1 OCK 3,100,031

PAWL ARRANGEMENT FOR HOIST Filed Nov. 2. 1960 IN VEN TOR. @f4/M d Loc/ VWM A Tmp/V67 United States Patent O 3,100,031 PAWL ANGEMENT FR HQHST Frank .1. Lock, Philadelphia, Pa., assigner to The Yale and Towne Manufacturing Company, Stamford, Conn., a corporation of Connecticut Filed Nov. 2, 1960, Ser. No. 66,796 1 Claim. (Cl. 18S-82.7)

'llhis invention relates to a chain hoist or puller of the type incorporating a one-way ratchet which is releasably connected to the load shaft of the hoist and cooperates with a pawl to prevent rotation of the load shaft in a direction to release 'a load.

In a hoist or puller of this type it is quite common to provide means for disengaging the pawl of the one-way ratchet to permit free rotation =of the load shaft in both directions. This allows slack in the hoist chain to be taken up, or other adjustments in the length of the chain to be made quickly and easily by manually pulling either end of the hoist chain. Once the slack is taken up, or other adjustments in the length of the chain have been made, the pawl is released `and lifting or pulling is effected by operation of the hoist through the usual operating lever or chain wheel.

'Ille present invention is directed to a pawl arrangement whereby a pawl concealed within the hoist housing may be quickly and easily disengaged from the ratchet by means provided on the exterior of the casing. One purpose of the invention is to provide such a pawl arrangement which is simple `and inexpensive, and which not only may be applied to new hoists, but may also be applied easily to existing hoists which do not include such an arrangement.

It is also a purpose of the invention to provide such an arrangement wherein the means on the exterior of the casing which are adapted to be actuated to release the pawl do not move with the pawl during normal operation of the ratchet, and, therefore, cannot interfere with the normal movement of the pawl in holding a load against dropping. To this end, the arrangement of the invention includes la pin which extends slidably through an opening in the hoist housing and has a lost motion connection with the pawl. This lost motion connection allows movement of the pawl relatively tothe pin during normal operation of the ratchet without movement of the pin or movement of means on the exterior of the housing for withdrawing the pin. When it is desired to disengage the pawl, the pin is merely withdrawn l.a suilicient `amount to iirst take up the lost motion and to lchen move the pawl away from the ratchet.

Other objects and advantages of the invention will become apparent from the following description, when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partial sectional view of a hoist incorporating the pawl arrangement of the invention, and showing the pawl engaged with the one-way ratchet,

FIG. 2 is a partial sectional view similar to that of FIG. 1, but showing the pawl disengaged from the oneway ratchet, and

FIG. 3 is a sectional View taken on the line 3-3 of FIG. 1.

Referring to the drawings, the pawl arrangement of the invention is shown applied to a hoist or puller of the type disclosed in U.S. Patent No. 2,165,984.

In a hoist of this type, la load supported on one end of a lifting chain -by means of a load hook 11 is lifted when `a brake hub member 12, best shown in FIG. 3, threaded on a `shaft 13, is rotated relatively to the shaft in -a clockwise direction, as viewed in FIG. l. The brake hub 12 is conveniently rotated by means of a lever 14 which is connected to the brake hub 12 means of a reversible pawl 15.

3,100,031 Patented Aug. 6, 1963 "ice Because of the threaded engagement between the brake hub 12 and the shaft 13, initial rotation `of the brake hub 12 in a clockwise direction results in endwise movement of the brake hub 12 relatively to the shaft 13 to force a one-way ratchet 16 lagainst a friction disc 17 and iiange member 18 to bind the one-way ratchet 16 to the shaft 13.

On continued rotation of the brake hub 12 in the clockwise direction, the one-way ratchet 16, shaft 13, friction disc 17, flange member 18 and brake hub 12 rotate as a unit. This clockwise rotation of the `shaft 13 results in counterclockwise rotation of a counter shaft 19 which is connected to the shaft 13 by means of a pinion 20 and .a gear 21 secured respectively to Kshaft 13 and the counter shaft 19. Counter shaft 19 has a sprocket 22 secured thereto over which lthe lifting chain 10 is trained, `and counterclockwise rotation of the counter shaft 19, therefore results in lifting of the lload hook 11 and any load supported thereby. Reverse rotation of the counter shaft 19 and shaft 13 in a load lowering direction by a load supported by the load hook 11 is prevented by engagement of a pawl 23 with teeth 24 of the one-way ratchet 16. The pawl 23 is conveniently mounted for pivotal movement on the end yof the countershaft 19 within the housing 25 of the hoist.

When it is `desired to lower a load carried by the load hook 11, the pawl 15 -of the lever 14 is reversed and the brake hub 12 rotated in a counterclockwise direction. This effects endwise movement of the brake hub 12 in a direction to relieve the braking action of the friction disc 17 on the one-way ratchet 16. The shaft 13 and shaft 19, therefore, slip relatively to the one-way rate-het d6 under the weight of the load on the lhook 11 to lower the load. The ratchet 16 is held again-st rotation in la lowering direction by engagement of the pawl 23 with the teeth 24. Such slippage of the shafts 13 and 19 and lowering of the load continues so llong as the brake hub 12 is rotated in a lowering direction at a greater speed than that at which the shafts 13 and 19 -are rotated by the load supported on the load hook 11.

If rotation of the brake hub 12 in the lowering direction is stopped, slight continued rotation of the shafts 13 and 19 by lthe load again effects endwise movement of the brake hub 12 in a direction .to bind the one-way ratchet 16 to the shaft 13 so that rotation of the shafts 13 and 19 in the 4lowering direction is stopped by engagement `of the pawl 23 with the teeth 24 of the oneway ratchet 16, and the load is ysafely held against dropping.

In accordance with the invention, a novel arrangement is provided for disengaging the pawl 23 from the oneway ratchet 16 so that when the reversible pawl 15 is disengaged from the brake hub 12, and the pawl 23 is disengaged from the one-way ratchet 16, as shown in FIG. 2, the shafts 13 and 19 may rotate freely in both directions and adjustments in the length of the chain 10 and the position of the load hook 11 may be made quickly and easily by manually pulling one end or the other of the chain 10.

As best shown in FIGS. l and 2, this arrangement for disengaging the pawl @3 from the one-way ratchet 16 includes a simple pin or rod 26 which extends slidably` through an opening 27 in the housing 25 and through an opening 28 in `the end of the pawl 23.

The pin 26 is provided with an enlarged head 29 at its extreme inner end which has a larger diameter than the opening 28 so that a pulling force applied to the pin 26 may be transmitted by the head 29 to the pawl 23. The opening 28 in the pawl 23 communicates with an enlarged opening or bore 30 of sufficient diameter to allow free movement of the head 29 so that the pawl 23 may move relatively to the pin 26. This arrangement provides a lost motion connection between the pawl `23 and the pin 26 so that the pawl may pivot to ride over the teeth 24 of the one-way ratchet 16 without etecting movement of the pin 26 as the ratchet 16 rotates in a clockwise direction during lifting of a load. VAt the same time, the pawl 2 3 may be completely disengagedrfrom the one-way ratchet 16 by withdrawing the pin 26 a suicient amount to take up the lost motion and to pivot the pawl 23 completely away from the teeth 24 of theA one-way ratchet 16.

The pawl 23 isurged toward the one-Way ratchet 26 by acoilspring 31 which surrounds the pin 26 and bears at one end against the pawl 23 and at the other end against the inner surface of the housing 25. The pin 26 is similar ly held in an inward position by means of a spring 32 so thatrit does not interfere with the normal movement of the pawl 23. The spring 32 bears at one end against the inner surface of the housing .25 and at the other end against a split ring retainer 33 which is seated in a suitable annular groove provided in the surface of the pin 26.

The pin 26 is adapted to be withdrawn to pivot the pawl 23 away from the one-way ratchet 16 against the force of the springs 31 and 32 by means of a toggle lever 34. The toggle lever 34 is pivotally attached to the outer end of the pin 26 on the exterior of the housing 25, and when the lever 34 is pivoted in a clockwise direction from the positionshown in FIG. 1 to the position shown in FIG. 2, the pin 26 is Withdrawn from the housing 25 to first take up the lost motion between it and the pawl 23 and then pivot thepawl. 23 away from the one-way ratchet 16, as shown in FIG. 2. When the lever 34 is pivoted to the position shown in FIG. 2, a flat surface 3S on the edge of the lever 34 engages the outer surface of the housing 25 so that the lever is held in this position by the compressed springs 31 and 32 and holds the pawl 23 away from the teeth 124 of the ratchet 16 until the lever 34 is again pivoted toward the position shown in FIG. 1. 1

-From the preceding description, it can be seen that there is provided a very simple arrangement for disengaging a pawl from a one-way ratchet of a hoist. The arrangement may be applied to new hoists, or may be easily applied to existing hoists merely by modifying such hoist by drilling holes through the housing and the pawl to accommodate the pin for withdrawing the pawl. Because of the lost motion connection between the pin and the pawl, neither the pin nor the lever for actuating the pin are moved by the pawl during normai operation of the one-way ratchet. The pin and lever cannot, therefore,

interfere with the normal movement of the pawl by the one-way ratchet so as to prevent the pawl from properly engaging the one-way ratchet to hold the load.

While one embodiment of the invention has been Shown and described, it will be appreciated that this is for the purpose of illustration and that changes and modifications can be made therein without departing from the spirit and scope of the invention.

-I now claim.

In a hoist having a housing, a ratchet mounted for rotation in said housing, a pawl mounted in said housing for movement into and out of engagement with said ratchet, an opening through said housing, a bore extending through said pawl substantially in alignment with said opening through said housing, a pin extending through and freely slidable in said opening, said pin having an outer end portion extending outwardly of said housing and an inner end portion slidable through said bore in said pawl, said inner end portion of said pin having a head of larger diameter than said bore in said pawl and providing a lost motion connection between the inner end of said pin and said pawl so that said pawl while in engagement with said ratchet may move freely relatively to said pin, a toggle lever pivoted to the outer end of said pin for rotation while engaged with the outside of said housing so that pull may be applied to said pin to withdraw said pawl from said ratchet, a spring extending between the inside of said housing surrounding said opening and a shoulder on said pin and acting through the pin to press the toggle lever against the outside of the housing, the spring pressure being eiective to hold said lever against rotation on its pivot While the pawl moves freely relativef 1y to the piu, and a second spring about said pin and said iirst spring and pressing between the inside Surface of said housing surrounding said opening and said pawl to urge said pawl toward the ratchet, the pressure of both said springs opposing movement of the toggle lever to Withdraw .said pawl and effective upon withdrawal of the pawl for holding said toggle lever against rotation on its pivot.

References Cited in the le of this patent Y UNITED STATES PATENTS 390,845 De Lamarre Oct. 9, 1888 1,025,088 Hess Apr. 30, 1912 1,331,697 Detzel Feb. 24, 1920 V1,368,796' Haas Feb. 15, 1921 1,974,333 Hirsch Sept. 18, 1934 

